A recent study suggested benefit of alpha tocopherol (Vitamin E) in slowing functional decline with cases of  mild to moderate Alzheimer Disease.  

Double-blind, placebo-controlled, parallel-group, randomized clinical trial involving 613 patients with mild to moderate AD was initiated in August 2007 and concluded in September 2012 at 14 Veterans Affairs medical centers.  Among patients with mild to moderate AD, 2000 IU/d of alpha tocopherol  resulted in slower functional decline when compared to the placebo group.

Abstract